Three-dimensional stress analysis and failure prediction in filled hole laminates

An observed stacking sequence effect [1] on pin bearing strength was examined by three-dimensional modeling. A displacement spline approximation method was used to perform the stress analysis. The laminate and the fastener were assumed to be linear elastic. Processing residual stresses were included in the analysis. The contact region and stress were unknown a priori and resulted from the solution. A nonuniform contact region through the thickness was allowed. Undamaged thermoelastic moduli were employed in the model. A stacking sequence effect on bearing strength was investigated by comparing stress distributions in two quasi-isotropic laminates of [0(2)/90(2)/45(2)/-45(2)](s) and [0(2)/45(2)/90(2)/-45(2)](s) stacking sequence. Stress magnitudes were displayed relative to ply strength properties. It was observed that all stress components, including the in-plane stresses, were affected by the stacking sequence. In the vicinity of the bearing plane, very high transverse shear stresses were found. A qualitative agreement between predicted stress distributions and experimental damage investigation, performed in Ref I. was demonstrated. Using a point stress failure criterion, a prediction of failure onset was performed. The predicted failure initiation load for the [0(2)/90(2)/45(2)/-45(2)](s) stacking sequence was approximately 40% higher than the predicted failure initiation load for the [0(2)/45(2)/90(2)/-45(2)](s) stacking sequence.